Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$49.39	4.406%	$51.5661	$51.57	$51.55	$51.60
Purchase #2	$190.44	9.337%	$208.2214	$208.22	$208.20	$208.20
Purchase #3	$82.57	5.722%	$87.2947	$87.29	$87.30	$87.30
Purchase #4	$156.59	5.142%	$164.6419	$164.64	$164.65	$164.60
Purchase #5	$24.76	10.596%	$27.3836	$27.38	$27.40	$27.40
Purchase #6	$35.66	3.134%	$36.7776	$36.78	$36.80	$36.80
Purchase #7	$111.72	5.258%	$117.5942	$117.59	$117.60	$117.60
7 purchase totals =	$651.13		$693.4795	$693.47	$693.50	$693.50